Looking for a quote for someone to alter bit of code on website running perl clasified adds software

I bought a program that was done in perl and it works great apart form one problem which in a sense makes the site fairly useless and people bought off no help. Its a classified adds progam and my problem is that when you add an add a drop down appears and you select the category from the drop down which is fine, (3 drop downs in all) the problem then appears in that you must then use the same drop down to then select a sub category and people are just not using doing this, they dont know you got to use samedrop down as such they dont use it and site not getting used propaly. The site is all pl and cgi files and i dont have a clue at all about this stuff. All i want to do is the user to be forced to use sub category so they cant move on to next drop down until they select the necessary sub from first. I cant be that much additional lines, they just need to be made to use the drop down until there are no more sub categories

The program was bought from mojoscripts and is the classifed package and they will not help me sort this out and there is no real work around except sort out script.

it would hopefully be someting simple and i would imagine you cant guess a quote without more details, i would duplicate site on a test server for you to play with.